Asm.js is still just JavaScript. Emscripten isn't currently production-grade software, and it still just compiles down to JavaScript.
I hope you understand that either of those options is still a case of using JavaScript. Are you seriously disputing that?
We can develop production-grade applications using Java, C, C++, C# and JavaScript for Android. We can only do a very small fraction of that when using Firefox OS. Firefox OS clearly provides far fewer viable options than Android does.
[1] https://en.wikipedia.org/wiki/Moving_the_goalposts